Energies and Atomic Structures of Grain Boundaries in Diamond: Comparison With Grain Boundaries in Silicon

1994 ◽  
Vol 339 ◽  
Author(s):  
M. Kohyama ◽  
H. Ichinose ◽  
Y. Ishida ◽  
M. Nakanose
Keyword(s):  
Thin Films ◽  
Grain Boundaries ◽  
Interfacial Energy ◽  
Atomic Structure ◽  
Tight Binding ◽  
Tilt Boundary ◽  
Atomic Structures ◽  
Fundamental Properties ◽  
Diamond Thin Films ◽  
First Time

ABSTRACTFairly different features of grain boundaries in diamond from those in Si were experimentally observed in diamond thin films. As the first step in order to understand the fundamental properties of grain boundaries in diamond, the energy and atomic structure of the {122} σ=9 tilt boundary have been calculated for the first time by using the tight-binding electronic theory. The results have been compared with the calculations of the same boundary and the {111} σ=3 boundary in Si. It has been shown that the σ=9 boundary in diamond has a very large interfacial energy caused by the large bond rigidity as compared with the boundaries in Si and the {111}σ=3 boundary in diamond. This point should be related to the observation that the {122}σ =9 boundary is rarely found in diamond thin films.

Dislocations, twins, and grain boundaries in CVD diamond thin films: Atomic structure and properties

1990 ◽  
Vol 5 (11) ◽  
pp. 2414-2423 ◽  
Author(s):  
J. Narayan
Keyword(s):  
Thin Films ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Atomic Structure ◽  
Boundary Energy ◽  
Stacking Faults ◽  
Annealing Treatment ◽  
Chemical Vapor ◽  
Chemical Vapor Deposition Diamond ◽  
Diamond Thin Films

We have used transmission electron microscopy techniques to study the nature of dislocations, stacking faults, twins, and grain boundaries in CVD (chemical-vapor-deposition) diamond thin films. Perfect a/2〈110〉 and partial a/6〈112〉 and a/3〈111〉 type dislocations are observed; the partial dislocations are also associated with twins and stacking faults. The most common defect in diamond thin films, particularly in 〈110〉 textured films, is Σ = 3 grain boundary or the primary twin. These twins in 〈110〉 textured films can lead to formation of fivefold microcrystallites. We have also investigated the splitting of Σ = 9 grain boundary (second order twin) into two Σ = 3 boundaries or primary twins via reaction Σ9 = 2Σ3. A rapid thermal annealing treatment has been shown to result in annealing of Σ = 3 boundaries and produce “defect-free” regions in thin films. A mechanism of annealing (removal) of Σ = 3 boundaries is discussed. Atomic structure and energetics of dislocations, twins, and grain boundaries are calculated using Tersoff potentials. The calculated atomic structure for Σ = 3 boundary is compared with high-resolution TEM images and a good agreement is obtained. These boundaries consist of periodic units of 5–7 rings which are similar to the core structure of 90° a/2〈110〉{001} dislocations. The energy of the 5–7 rings in the grain boundaries is considerably lower, due to overlapping and strain cancellation effects, than that associated with single dislocations. The 5–7 ring energy and consequently the boundary energy increases as the overlapping effects decrease. An interesting analogy between the diamond and silicon results is drawn.

Atomic structure of [0001]-tilt grain boundaries in ZnO:  A high-resolution TEM study of fiber-textured thin films

2004 ◽  
Vol 70 (12) ◽  
Author(s):  
Fumiyasu Oba ◽  
Hiromichi Ohta ◽  
Yukio Sato ◽  
Hideo Hosono ◽  
Takahisa Yamamoto ◽  
...  
Keyword(s):  
Thin Films ◽  
High Resolution ◽  
Grain Boundaries ◽  
Atomic Structure ◽  
High Resolution Tem

Dislocations, twins, grain boundaries and interfaces in diamond CVD thin films: Atomic structure and properties

Carbon ◽  
1990 ◽  
Vol 28 (6) ◽  
pp. 775 ◽  
Author(s):  
J. Narayan ◽  
A.S. Nandedkar ◽  
G. Matera ◽  
M. Lango ◽  
A. Rengan ◽  
...  
Keyword(s):  
Thin Films ◽  
Grain Boundaries ◽  
Atomic Structure ◽  
Structure And Properties

Structural multiplicity in a tilt boundary in germanium

1988 ◽  
Vol 46 ◽  
pp. 592-593
Author(s):  
D.A. Smith ◽  
Z. Elgat ◽  
W. Krakow ◽  
A.A. Levi ◽  
C.B. Carter
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Twin Boundary ◽  
Atomic Structure ◽  
Czochralski Method ◽  
Tilt Boundary ◽  
Considerable Progress ◽  
Related Structure ◽  
First Order ◽  
Impurity Segregation

There has been considerable progress made recently in understanding the atomic structure of grain boundaries in metals, semiconductors and ceramics. There is still, however, some dispute over whether a given grain boundary can exist with more than one non-symmetry-related structure. This has been shown experimentally to be the case in Ge for the first-order twin boundary lying parallel to the lateral {112} plane. In the present paper, it will be shown that a similar result holds for a more general grain boundary (actually Σ=137) lying close to the Σ=19 orientation; the Σ=19 boundary is formed by a rotation of 26.5° about a common <110> direction and lies along a common {31} plane. It is thus likely that a similar result will hold for other grain boundaries.Since it is essential to know that the different structures are not due to impurity segregation effects, bicrystals were grown from the melt with pre-oriented seeds using the Czochralski method following the approach of Bacmann as modified at Cornell by Skrotzki et al.

Atomic Structures and Defects of As-Grown Nb1+αS2 Platelets on Nb Substrates

1992 ◽  
Vol 295 ◽  
Author(s):  
Chuxin Zhou ◽  
L. W. Hobbs
Keyword(s):  
Crystal Structure ◽  
Grain Boundaries ◽  
Diffraction Pattern ◽  
Atomic Structure ◽  
Stacking Faults ◽  
Planar Defect ◽  
Defect Structures ◽  
Planar Defects ◽  
Atomic Structures ◽  
Octahedral Sites

AbstractThe interlocking of Nb1+αS2 platelets developed during sulfidation of Nb results in formation of a compact scale. The atomic structure and defects of these platelets were investigated using HREM. The resulting microstructure is very different from conventional microstructure consisting of polygonal grains and polyhedral grain boundaries because of the anisotropy of the crystal structure. The principal phase was identified as 3R-Nb2+αS2 intergrown with 2H-Nb1+αS2, or with some other arrangement of S-Nb-S slabs. The -S6- octahedral sites between two S-Nb-S slabs provide accommodation for extra Nb or foreign atoms and the large non-stoichiometry of Nb1+αS2. Stacking faults along the c axis account for the high density of planar defect structures observed within almost every platelet. Axial lattice fringe images and streaking in the diffraction pattern indicate that the planar defects are normal to the c direction.

scholarly journals Morphology and Electron Emission Properties of Nanocrystalline CVD Diamond Thin Films

1997 ◽  
Vol 495 ◽  
Author(s):  
Alan R. Krauss ◽  
Dieter M. Gruen ◽  
Daniel Zhou ◽  
Thomas G. Mccauley ◽  
Lu Chang Qin ◽  
...  
Keyword(s):  
Thin Films ◽  
Grain Size ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Hydrogen Concentration ◽  
Electron Emission ◽  
Microwave Plasma ◽  
Initial Growth ◽  
Average Grain Size ◽  
Diamond Thin Films

ABSTRACTNanocrystalline diamond thin films have been produced by microwave plasma-enhanced chemical vapor deposition (MPECVD) using C60/Ar/H2 or CH4/Ar/H2 plasmas. Films grown with H2 concentration ≤ 20% are nanocrystalline, with atomically abrupt grain boundaries and without observable graphitic or amorphous carbon phases. The growth and morphology of these films are controlled via a high nucleation rate resulting from low hydrogen concentration in the plasma. Initial growth is in the form of diamond, which is the thermodynamic equilibrium phase for grains < 5 nm in diameter. Once formed, the diamond phase persists for grains up to at least 15–20 nm in diameter. The renucleation rate in the near-absence of atomic hydrogen is very high (∼1010 cm2sec−1), limiting the average grain size to a nearly constant value as the film thickness increases, although the average grain size increases as hydrogen is added to the plasma. For hydrogen concentrations less than ∼20%, the growth species is believed to be the carbon dimer, C2, rather than the CH3* growth species associated with diamond film growth at higher hydrogen concentrations. For very thin films grown from the C60 precursor, the threshold field (2 to ∼60 volts/micron) for cold cathode electron emission depends on the electrical conductivity and on the surface topography, which in turn depends on the hydrogen concentration in the plasma. A model of electron emission, based on quantum well effects at the grain boundaries is presented. This model predicts promotion of the electrons at the grain boundary to the conduction band of diamond for a grain boundary width ∼3–4 Å, a value within the range observed by TEM.

scholarly journals Effect of Ordering Energy on Grain Boundary Structure in L12 Alloys

1988 ◽  
Vol 133 ◽  
Author(s):  
G. J. Ackland ◽  
V. Vitek
Keyword(s):  
Grain Boundaries ◽  
Tight Binding ◽  
Structural Features ◽  
Boundary Structure ◽  
Many Body ◽  
Atomic Structures ◽  
Empirical Potentials ◽  
Grain Boundary Structure ◽  
Moment Approximation ◽  
Ordered Alloys

ABSTRACTAtomic structures of grain boundaries in two L12 ordered alloys with very different ordering energies have been calculated. The interatomic forces are represented by many-body empirical potentials based on the second moment approximation to the tight-binding density of states. Grain boundaries in strongly ordered alloys show very little relaxation. This results in the presence of columns of cavities in the boundaries. On the other hand boundaries in weakly ordered alloys, and also in pure f.c.c. materials, show extensive relaxations leading to much more homogeneous structures. We suggest that these structural features may be responsible for the intrinsic brittleness of grain boundaries in compounds such as Ni3Al in contrast with boundaries in pure f.c.c. metals or ordered alloys such as Cu3Au which are only embrittled by segregation.

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